solutions 1/2008 – Additional informations

A complex manufacturing process: the final disks of the
highest purity are made from calcium fluoride crystals that often weigh 100 kilograms.
Photo: SCHOTT

Growing of monocrystals is unique

Calcium fluoride blanks are made from fine powder that needs to be as pure as possible. The first step calls for this powder to be melted down so that the crystallization process can begin. In order to reduce the tension that results from the extreme differences in temperature as much as possible, the temperature has to be lowered extremely slowly.

This is why the crystal growing facilities at schott operate under a high vacuum using a highly sophisticated temperature program that enables extremely slow, yet disturbance-free growth of the crystals by only a few centimeters per day. The grown crystals that often weigh 100 kilograms are then removed after a few weeks. These have a diameter of up to 350 millimeters and a thickness of at least 150 millimeters. During the next stage of production, the two end regions are cut off perfectly parallel to the growth region and this results in the final blanks. Despite the considerable dimensions that were never possible before, the atomic structure is completely identical. This is also why they are referred to as monocrystals. SCHOTT is the only vendor in the world that is capable of producing crystals with such diameters in incomparable purity and has access to the world’s largest manufacturing capacity.